1.Technical Field of the Invention
The present invention relates to enhancing the solubility in solvent media, notably alcoholic media, of the beta-hydroxy acids (“BHAs”), notably the chemical skin peel salicylic acid, by intimately admixing same with at least one alpha-hydroxy acid (“AHA”), for example lactic acid, glycolic acid, citric acid, and the like.
This invention also relates to the formulation of higher potency BHA skin peel products, advantageously formulated as gels.
2.Description of the Prior Art
It is known to this art that the beta-hydroxy acids such as salicylic acid exhibit keratolytic activity in the skin and are useful superficial chemical skin peels. Compare WO 97/28786 and references cited therein, each of which hereby being expressly incorporated by reference. Cf. U.S. Pat. Nos. 4,954,487, 5,296,476, 5,449,519 and 6,410,036.
Salicylic acid, or 2-hydroxybenzoic acid, has the structural formula:
and its maximum solubility in alcohol is roughly on the order of 29%. It is described in the 13th Edition of the Merck Index (2001) at pages 1495-1496,Item No. 8411 (also expressly incorporated by reference), as are various of the clinical indications thereof, e.g., treatment of warts and corns, acne, as an anti-inflammatory, analgesic, antipyretic.
WO 97/28786 describes a method for effecting a superficial chemical skin peel by topically applying to skin to be treated, usually facial skin, a composition containing at least 15% by weight of salicylic acid, in a dermatologically acceptable liquid solvent.
Such superficial chemical skin peels are useful for the treatment of a variety of skin disorders, for example photodamaged skin, hyperpigmentation, acne vulgaris, rosacea, premalignant skin cancer, wrinkles and fine lines, superficial scars and the like.
While WO 97/28786 mandates salicylic acid concentrations of at least 15% by weight, even suggesting “most preferably . . . at least 30 wt. % ,” to provide the desired efficacy, such concentrations are nonetheless limited to the saturation concentration of the salicylic acid in the particular solvent.
Need, therefore, continues to exist for even more concentrated BHA chemical skin peels.